Blood oxygenator



H. F. EVERETT BLOOD OXYGENATOR Feb. 3, 1970 Filed Dec.

2 Sheets-Sheet 1 FIG].

INVENTOR HAZEN F. EVERETT AT TORNE Y 1970 H. F. EVERETT BLOOD OXYGENATOR 2 Sheets-Sheet 2 Filed Dec. 12, 1967 FIG. 2.

we/won HAZEN F. EVERETT ATTORNEY United States Patent 3,493,347 BLOOD OXYGENATOR Hazen F. Everett, 120 Bedford Road, Hillsdale, NJ. 07642 Filed Dec. 12, 1967, Ser. No. 689,855 Int. Cl. A61m 1/03 US. Cl. 23258.5 11 Claims ABSTRACT OF THE DISCLOSURE A blood oxygenator is provided with elongated, substantially vertical tube-like elements having lateral openings distributed along the length thereof and constituting at least fifty percent of the area of each element, and venous blood is introduced to the interior of each element at the upper end thereof for the gravity induced flow to the lower end of the element, during which flow the blood films across the lateral openings for oxygenation by an oxygen-rich atmosphere in which the tube-like elements are disposed.

This invention relates generally to blood oxygenators, that is, apparatus for oxygenating blood, as during cardiopulmonary bypass.

Blood oxygenators now in use have one or more disadvantageous characteristics, such as, large priming volume, inefficient exchange of oxygen and carbon dioxide so that oxygenation of the blood cannot be completed during a single pass through the apparatus, the turbulent frothing of bubbles through the blood so that anti-foam agents are required, and subjection of the blood to undesirable trauma so that the cardio-pulmonary bypass can be safely maintained for only a limited time thereby restricting the surgical procedures that can be performed.

Accordingly, it is an object of this invention to provide a blood oxygenator that will permit long, safe cardiopulmonary bypass.

Another object is to provide a blood oxygenator in which the exchange of oxygen and carbon dioxide is so efficiently performed as to complete the oxygenation of the blood during a single pass therethrough and with minimum trauma to the blood.

Another object is to provide a blood oxygenator having a minimal priming volume so as to minimize or completely eliminate the need for transfusion blood in initiating the operation of the oxygenator.

In accordance with this invention, a blood oxygenator is provided with elongated substantially vertical tube-like elements having lateral openings distributed along the length thereof to constitute at least fifty percent of the area of the element, and such tube-like elements are dis posed in an oxygenrich atmosphere so that, when venous blood is introduced into the upper ends of the elements for gravity induced fiow therein, such blood films across the openings for oxygenation by the surrounding atmosphere.

In order to encourage recirculation of the red cells in the plasma for more efficient exposure to the oxygen, the openings in each tube-like element are preferably disposed in staggered, over-lapping relation in opposite sides of the element.

The above, and other objects, features and advantages of this invention, will be apparent in the following de tailed description of illustrative embodiments thereof which is to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of a blood oxygenator according to this invention shown with a side wall of its housing removed;

Patented Feb. 3, 1970 FIG. 2 is an enlarged, fragmentary perspective view illustrating one of the frames and several blood filming elements included in the oxygenator;

FIG. 3 is a detail, sectional view of one of the filming elements and its connection to a respective feeder passage by which venous blood is supplied thereto;

FIG. 4 is a view similar to that of FIG. 3, but illustrating another embodiment of the invention;

FIG. 5 is an enlarged, fragmentary perspective view showing details of a filming element in accordance with this invention;

FIG. 6 is an elevational view of a tube from which a filming element in accordance with another embodiment of this invention can be formed by longitudinal expansion thereof;

FIG. 7 is an elevational view of a filming element formed by longitudinal expansion of the tube of FIG. 6;

FIG. 8 is an elevational view of a helical spring; and

FIG. 9 is an elevational view of a filming element according to this invention formed by permanent deformation of the opening of FIG. 8.

Referring to the drawings in detail, and initially to FIG. 1 thereof, it will be seen that a blood oxygenator 10 in accordance with this invention may generally comprise a housing 11 constituted by a base 12 and an upper portion 13. The base 12, which may be formed of stainless steel, is shown to have spaced sides 14 between which there extends a wall 15 that is inclined downwardly toward the rear of the housing. Wall 15 cooperates with a wall 16 spaced downwardly therefrom to define a compartment 17 therebetween through which hot water or any other heating medium, or a cooling medium may be circulated by way of an inlet 18 and an outlet 19 to heat the surface of wall 15. A well or sump 20 is provided adjacent the back edge of inclined wall 15 to constitute a reservoir for oxygenated blood draining from wall 15. An outlet 21 extends from the bottom of well 20 for returning oxygenated or arterial blood to a patient by way of flexible tubing and a suitable pump (not shown) interposed therein. The outlet 21 may extend from the side of well 20 which is remote from wall 15 with a vertical screen or strainer 22 extending across well 20 so that all oxygenated blood received by well 20 from inclined wall 15 must pass through strainer 22 on its way to outlet .21.

The upper portion 13 of housing 11 may rest removably on base 12 and have front, back and side walls 23, 24 and 25, respectively, and a removable lid 26 formed of a suitable transparent plastic, such as, methyl methacrylate. The lid 26 may be provided with screened Vent openings 27 to permit the escape of carbon dioxide and excess oxygen from within housing 11. Oxygen is supplied to the interior space or chamber in housing 11 by way of flexible tubes (not shown) connected to hose fittings 28 which extend through front wall 23 are connected to tubes or oxygen manifolds 29 extending along the inner surface of side walls 25 adjacent the lower edges thereof. Such tubes 29 have perforations 30 spaced apart therealong and from which the oxygen can issue for dispersal within housing 11 so as to create an oxygen-rich atmosphere therein.

Venous blood to be oxygenated is brought from the patient to the oxygenator 10 by way of at least one flexible tube 31 which is connected to a hose fitting 32 at one end of a horizontal manifold 33 extending from front to back along the upper portion of one of side walls 25. The manifold 33 has a number of spaced apart ports 34 opening through the adjacent side wall 25, and through which venous blood can be supplied to one or more blood filming assemblies 35.

As shown on FIGS. 1 and 2, each assembly 35 generally comprises a rectangular frame 36, a number of filming elements 37, a supply duct 38 common to all of the filming elements in the assembly 35 and individual feeder passages 39 extending from supply duct 38 to the several filming elements. Each frame 36 may have its side portions slidably received between vertical guides 40 which project from the inner surfaces of side walls 25. Thus, assemblies 35 can be introduced in, or removed from housing 11 by vertical sliding movements of the respective frames 36 between guides 40 to either increase or decrease the capacity of oxygenator 10.

The common supply duct 38 of each assembly 35 extends horizontally across the respective frame 36 at a position spaced downwardly from the top of the frame and is open at one end to be inserted in a port 34 for receiving venous blood from manifold 33. The feeder passages 39, which are shown defined by individual tubes in the embodiment of FIGS. 1, 2 and 3, extend upwardly from common duct 38 over the top of frame 36 and then downwardly to open into the upper ends of the respective filming elements 37.

In accordance with this invention, each filming element 37 is of elongated, tube-like configuration and is suspended substantially vertically so that venous blood from the respective feeder passage 39 enters the interior of tube-like element 37 at the upper end of the latter and is made to fiow by gravity along element 37 for discharge at the lower end of the latter. As shown on FIG. 1, the tubelike elements 37 may be dimensioned so that the lower ends thereof are spaced upwardly from inclined wall of the base 12, or the elements 37 may be dimensioned to contact wall 15.

As shown particularly on FIG. 5, each of tube-like elements 37 in accordance with this invention has lateral openings 41 distributed along the length thereof with the aggregate area of openings 41 being at least 50% of the total area of tube-like element 37. The successive openings 41 of element 37, considered in the direction of the longitudinal axis of the latter, are angularly displaced relative to each other, for example, disposed in staggered relation at diametrically opposed sides of element 37, as shown, and the successive openings are further preferably overlapped in the longitudinal direction of the element. Further, as shown, the openings 41 are preferably notchshamd, that is, V-shaped when viewed from the side, as on FIG. 3.

Each of filming elements 37 may be conveniently formed of a tube of surgical grade polyvinyl chloride, polypropylene, polyethylene tetraphthalate, polytetrafluoroethylene or other suitably inert plastic material, or of a non-reactive metal, such as, stainless steel, in which the notch-shaped openings 41 are suitably cut.

Alternatively, as indicated on FIG. 6, a tube 37a of stainless steel or other non-reactive metal may be cut part-way through, alternatively from diametrically opposed sides thereof, in planes normal to the longitudinal axis, as at 42 and 43, and then longitudinally expanded, as on FIG. 7, to provide an elongated tube-like element 37b having the staggered arrangement of notch-shaped openings 41b for use in accordance with this invention.

Further, as shown in FIG. 8, a helical spring 370 of stainless steel or other non-reactive metal may have successive coils angularly or trosionally displaced relative to each other beyond the elastic limit of the Spring material so that such successive coils will remain in angularly displaced or deformed positions relative to each other, as shown on FIG. 9, to define a tube-like element 37d constituted by the permanently deformed coils or turns of the spring which define notch-shaped openings 41d in staggered, overlapping relation at opposite sides of the element.

When venous blood is introduced to the interior of an element 37, 37b or 37d in accordance with this invention for gravity induced flow downwardly through the element from its upper end, the blood films across openings 41, 411) or 41d for exposure to the oxygen-rich atmosphere within housing 11. Since the lateral openings 41 of the tube-like element are staggered at opposite sides thereof, such openings support a zig-zag pattern of films so that the blood moves downwardly in a non-linear path to encourage recirculation of the red cells within the plasma for most efiicient exposure to oxygen.

Each of filming elements 37 may have an inner diameter in the range from approximately .10 inch to .25 inch, while the corresponding feeder passage 39 preferably has a relatively smaller inner diameter so as to meter the flow of venous blood to the respective filming element. For example, when each filming element has an inner diameter of .125 inch, effective metering of the supply of venous blood thereto is achieved with a feeder passage having an inner diameter of .0625 inch.

In the embodiment of the invention illustrated by FIGS. 1, 2 and 3, the feeder passages 39 are defined by individual tubes and the several filming elements 37 have their upper ends cemented or otherwise directly attached to the ends of such tubes remote from common duct 38. However, as shown on FIG. 4, all of the feeder passages, one of which is indicated at 39a, may be defined by laterally spaced passages in a single structure 139 extending from the common duct 138, with the ends of the several passages 39a remote from duct 138 being spaced from the upper ends of the respective filming elements 37, as by the distance d, so that the metered blood supplied through each feeder passage 39a can form into discrete drops which fall successively into the upper adjacent end of the respective filming element 37.

In using the blood oxygenator 10 embodying this invention, the patient constituting the source of venous blood is disposed at an elevation above the top of housing 11 so that the venous blood supplied through tube 31 and manifold 33 to the common duct 38 of each of the assemblies 35 within the housing 11 will have a pressure head substantially greater than the distance D (FIG. 2) that each of feeder passages 39 rises above the respective common duct 38. Each of feeder passages 39 is dimensioned, as previously indicated, so that the rate of flow therethrough under suchpressure head will substantially correspond to the rate at which the respective filming element 37 can complete the exchange of oxygen and carbon dioxide during the flow of blood along the length of such element. Thus, the blood discharged from the lower end of each element 37 will be fully oxygenated. Further, the indicated small diameter of each feeder passage 39 and its rise to the distance D above the common supply duct 38 appears to create a sufiicient back pressure in each of the feeder passages to ensure the substantially uniform supplying of blood from each duct 38 to all of the feeder passages connected therewith. Thus, during operation of oxygenator 10, all of the filming elements 37 of each assembly 35 installed within housing 11 are fully and equally utilized for the efiicient oxygenation of the venous blood supplied to the oxygenator. It is a characteristic of the described arrangement, that the relatively small pressure of venous blood supplied to the oxygenator 10 from the patient is suflicient to start the oxygen'ating action in all of the filming elements 37 which are wet by very small volumes of blood so that there is no need to prime the oxygenator with blood prior to the initiation of its operation.

In a particular example of an oxygenator in accordance with this invention, each filming element 37 has an oxygenating capacity of approximately 10 cubic centimeters per minute, and fifty of the filming elements 37 are provided on each frame 36 to receive venous blood from a common supply duct 38 by way of the individual feeder passages 39. Thus, in such example, each assembly 35 has an oxygenating capacity of approximately 500 cubic centimeters per minute, and the number of assemblies 35 installed within housing 11 is selected so as to correspond to the oxygenating capacity required for a particular patient.

In the arrangement shown on FIG. 1, three assemblies 35 are installed Within housing 11, in which case the oxygenator will have a total capacity of 1500 cubic centimeters per minute. Of course, it will be understood that the ports 34 opening from manifold 33 at locations where assemblies 35 are absent will be suitably plugged to ensure that all of the supplied venous blood passes through the filming elements 37. In the particular example of this invention mentioned above, the housing 11 is adapted to accommodate a maximum of twelve assemblies 35 so that the oxygenating capacity can be readily varied from a minimum of 500 cubic centimeters per minute to a maximum of 6 liters per minute.

The fully oxygenated blood drips or flows equally from the lower ends of all of the filming elements 37 onto the underlying inclined surface 15 which is heated and spreads in a relatively thin film over such surface 15 for efficient heat exchange with the latter.

Since there are no relatively moving parts in the oxygenator 10 and the blood being oxygenated merely flows downwardly through the elements 37 so as to film across the lateral openings thereof, there is minimal turbulence of the blood throughout the oxygenator and the entrainment of bubbles in the blood is minimized. This permits the use of a small reservoir for the arterial or oxygenated blood so that the total volume of blood within the oxygenator 10 during its operation is reduced to a minimum. It has further been found that the non-turbulent, gentle operation of the oxygenator in accordance with this invention, and the fact that oxygenation of the blood is completed during a single pass through the filming elements 37 results in minimal trauma to the blood and thereby makes it possible to safely maintain a cardiopulmonary bypass for extremely long periods of time.

Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention, except as defined in the appended claims.

What is claimed is:

1. In a blood oxygenator having a housing adapted to contain an oxygen-rich atmosphere and means to supply venous blood to the interior of the housing, an elongated, substantially vertical tube-like element having lateral openings distributed along the length thereof and being adapted to be disposed in said oxygen-rich atmosphere,

the aggregate portion of the surface area of said element which is occupied by said openings being at least fifty percent of the total surface area of said tube-like element so that when said venous blood is introduced to the interior of said tube-like element at the upper end thereof for gravity induced flow along the element, such blood films across said openings for oxygenation by the surrounding oxygen-rich atmosphere.

2. In a blood oxygenator, a tube-like element according to claim 1, in which said lateral openings are disposed in staggered relation to each other at opposite sides of said element.

3. In a blood oxygenator, a tube-like element according to claim 2, in which said openings at one side of the tube are in overlapping relation to the openings at the other side of the tube considered in the direction of the longitudinal axis of said element.

4. In a blood oxygenator, a tube-like element according to claim 1, in which successive openings of said element, considered in the direction of the longitudinal axis of the latter, are angularly displaced relative to each other about said axis and overlapped in said direction.

5. In a blood oxygenator, a tube-like element according to claim 4, in which each of said openings is notch-shaped.

6. A blood oxygenator comprising a housing adapted to contain an oxygen-rich atmosphere, a plurality of elongated, substantially vertical tube-like elements suspended in said housing, each of said tube-like elements having lateral openings distributed along the length thereof, the aggregate portion of the surface area of said element which is occupied by said openings being at least fifty percent of the total surface area of said tube-like element, means for introducing venous blood to the interior of said tube-like elements at the upper ends thereof for gravity induced flow along the elements during which the blood films across said openings for oxygenation by the surrounding oxygen-rich atmosphere, and means to collect oxygenated blood discharged from the lower ends of said elements.

7. A blood oxygenator according to claim 6, in which said means to collect oxygenated blood includes an inclined surface spaced downwardly from said lower ends of the tube-like elements and means defining a reservoir for oxygenated blood adjacent the lowermost side of said surface.

8. A blood oxygenator according to claim 7, in which said inclined surface is defined by a wall of a compartment through which a heating medium is circulated.

9. A blood oxygenator according to claim 6, in which at least certain of said tube-like elements are arranged side-by-side, and said means for introducing venous blood to said certain elements includes a common venous blood supply duct directed horizontally across said certain elements below said upper ends thereof and adapted to reeive venous blood from a source at an elevation substantially above said upper ends, and means defining individual feeder passages extending upwardly from said common supply duct and each opening adjacent the upper end of a respective one of said tube-like elements to discharge venous blood into the respective element at a rate substantially equal to that at which the blood can be oxygenated during travel along the length of said element.

10. A blood oxygenator according to claim 9, in which each of said feeder passages opens at a distance above the upper end of the respective tube-like element so that the venous blood discharged from each feeder passage falls in drops into the upper end of the respective tube-like element.

11. A blood oxygenator according to claim 9, in which said feeder passages extend upwardly from said common supply duct to an elevation higher than that of said upper ends of the tube-like elements.

References Cited UNITED STATES PATENTS 12/1962 Wild et a1 23258.5 10/1965 Galajda 23258.5

U.S. Cl. X.R. 

